1. Field of the Invention
The present invention is directed to fasteners and more specifically to sheet metal fasteners which are designed for use in the roofing industry to secure felt, insulation or roofing membranes to underlying cementitious and/or composite materials such as, but not limited to, gypsum, Tectum.RTM. and other fibrous decking. The invention includes a generally hollow tapered compaction shank through which a wire staple is driven to provide an anchor to prevent withdrawal of the fastener once in place.
2. Brief Description of the Related Art
In the roofing industry, and especially in commercial roofing, gypsum, Tectum.RTM. light-weight concrete and other cementitious and/or composite materials are utilized to form a roofing deck. In order to make the deck weather resistant, felts, plastics or other types of membranes and insulating materials may be placed over the roofing deck. A recovery board or other material layer may be placed over the materials covering the roof deck composite and are secured thereto utilizing fasteners which are specifically designed to retain the materials to the roof deck material even under high wind conditions. After the fasteners have been installed they may be covered with an asphalt type material or other adhesive or plastic.
Early fasteners utilized in roofing installations included fasteners made of sheet metal having spreadable legs which, when driven into cementitious, composite, or other roof deck material, would deform or deflect relative to one another to thereby capture a plug of the material therebetween. The captured plug resisted back-out or pull-out of the fasteners. To improve the manner in which sheet metal fasteners distributed their holding force to an underlying membrane, fabric or other material layers, such fasteners were modified to include large disks. Such disks serve to distribute the force of the head of the fasteners over a greater area and thus reduce the chance of membrane tears, especially under adverse wind conditions.
In an effort to improve upon the holding resistance of fasteners utilized in the roofing industry, other developments have been made in fasteners which include locking wires. In U.S. Pat. Nos. 4,456,416 and 4,611,964 to Schlein, anchoring nails are disclosed which include a generally cylindrical nail shank which is hollow and which has an opening adjacent the lower end thereof through which a barbed end of an insert wire extends. The barbed end of the wire curves upwardly when driven through the hollow nail shank. In use, the nail shank is initially driven within a roof deck material, after which, the locking wire is driven through the shank such that the end barb hooks outwardly within the material to thereby provide increased anchoring.
Other types of fasteners have been developed utilizing a separate anchoring wire. A screw fastener has been developed which is formed of a nylon material and which includes a generally U-shaped staple locking wire which is driven centrally of the fastener. The wire includes a pair of barbed ends for extending outwardly from adjacent the tip of the fastener when the staple is driven through the fastener. The screw fastener must first be inserted into a decking material which often requires a boring hole to accept the screw. Such structures are disclosed, by way of example, in U.S. Pat. No. 4,655,659 to Leemke.
In the roofing industry, it is critical that fasteners be easily installed with minimum work effort and yet remain rigidly anchored once in place. Any back-out of the fasteners can result in damage to the roof and expensive maintenance problems. In areas where high wind conditions exist, such as in areas where hurricane wind forces can be expected, winds can destroy a roof if the fasteners fail to provide sufficient retention force to secure the roofing materials. For this reason, fasteners utilized in the roofing industry are tested and must be approved for use by regulatory agencies.
Other examples of fasteners which incorporate a generally hollow body through which a wire staple may be driven are disclosed in U.S. Pat. Nos. 1,039,531 to Hartley, 1,075,911 to Gobin, 1,428,111 to Molesworth and 1,548,456 to Goodman. However, such fasteners are not designed for use in the roofing industry.